Imprint lithography

ABSTRACT

A lithographic apparatus is disclosed that has a first substrate table arranged to hold a substrate and a second substrate table arranged to hold a substrate, an imprint template holder arranged to hold an imprint template, and an imprintable medium dispenser, wherein the first substrate table is moveable between a first position located at or adjacent to the imprintable medium dispenser, and a second position located at or adjacent to the imprint template holder, and the second substrate table is moveable between the first and second positions, such that the first and second substrate tables swap positions.

This application is a continuation of U.S. patent application Ser. No.13/198,425, filed Aug. 4, 2011, now allowed, which is a continuation ofU.S. patent application Ser. No. 11/364,497, filed on Mar. 1, 2006, nowU.S. Pat. No. 8,011,915, which claims the benefit of priority of U.S.Provisional Patent Application No. 60/733,175, filed on Nov. 4, 2005,each of the foregoing applications is hereby incorporated in itsentirety by reference.

FIELD

The present invention relates to imprint lithography.

BACKGROUND

A lithographic apparatus is a machine that applies a desired patternonto a target portion of a substrate. Lithographic apparatus areconventionally used, for example, in the manufacture of integratedcircuits (ICs), flat panel displays and other devices involving finestructures.

It is desirable to reduce the size of features in a lithographic patternbecause this allows for a greater density of features on a givensubstrate area. In photolithography, the increased resolution may beachieved by using radiation of shorter wavelength. However, there areproblems associated with such reductions. Current systems are startingto adopt optical sources with wavelengths in the 193 nm regime but evenat this level, diffraction limitations become a barrier. At lowerwavelengths, the transparency of materials is very poor. Opticallithography machines capable of enhanced resolutions require complexoptics and rare materials and are consequently very expensive.

An alternative for printing sub-100 nm features, known as imprintlithography, comprises transferring a pattern to a substrate byimprinting a pattern into an imprintable medium using a physical mouldor template. The imprintable medium may be the substrate or a materialcoated on to a surface of the substrate. The imprintable medium may befunctional or may be used as a “mask” to transfer a pattern to anunderlying surface. The imprintable medium may, for instance, beprovided as a resist deposited on a substrate, such as a semiconductormaterial, into which the pattern defined by the template is to betransferred. Imprint lithography is thus essentially a moulding processon a micrometer or nanometer scale in which the topography of a templatedefines the pattern created on a substrate. Patterns may be layered aswith optical lithography processes so that, in principle, imprintlithography could be used for such applications as IC manufacture.

The resolution of imprint lithography is limited only by the resolutionof the template fabrication process. For instance, imprint lithographymay be used to produce features in the sub-50 nm range withsignificantly improved resolution and line edge roughness compared tothat achievable with conventional optical lithography processes. Inaddition, imprint processes do not require expensive optics, advancedillumination sources or specialized resist materials typically requiredby optical lithography processes.

SUMMARY

According to a first aspect of the present invention there is providedan imprint lithography apparatus, comprising a first substrate tablearranged to hold a substrate; a second substrate table arranged to holda substrate; an imprint template holder arranged to hold an imprinttemplate; and an imprintable medium dispenser, wherein the firstsubstrate table is moveable between a first position located at oradjacent to the imprintable medium dispenser, and a second positionlocated at or adjacent to the imprint template holder, and wherein thesecond substrate table is moveable between the first and secondpositions, such that the first and second substrate tables swappositions.

According to a second aspect of the invention there is provided animprint lithography apparatus comprising a first substrate tablearranged to hold a substrate; a second substrate table arranged to holda substrate; an imprint template; and a dispenser configured to dispenseimprintable medium, wherein the first substrate table is moveablebetween a first position located at or adjacent to the imprintablemedium dispenser, and a second position located at or adjacent to theimprint template, and the second substrate table is moveable between thefirst and second positions, such that the first and second substratetables swap positions.

According to a third aspect of the invention there is provided animprint lithography apparatus, comprising a substrate table arranged tohold a substrate; an imprint template holder arranged to hold an imprinttemplate; and at least two imprintable medium dispensers, a first of theimprintable medium dispensers located at or adjacent to one side of theimprint template holder, and a second of the imprintable mediumdispensers located at or adjacent to an opposite side of the imprinttemplate holder.

According to a fourth aspect of the invention there is provided animprint lithography apparatus, comprising a substrate table arranged tohold a substrate; an imprint template; and at least two imprintablemedium dispensers, a first of the imprintable medium dispensers locatedat or adjacent to one side of the imprint template, and a second of theimprintable medium dispensers located at or adjacent to an opposite sideof the imprint template.

According to a fifth aspect of the invention there is provided animprint lithography process, comprising moving a first substrate tableholding a first substrate to a first position; aligning the substrate tothe substrate table at the first position; dispensing an imprintablemedium layer on the first substrate at the first position; moving thefirst substrate to a second position; moving a second substrate tableholding a second substrate to the first position; pressing, at thesecond position, one or more templates in the imprintable medium layer;and aligning the second substrate to the second substrate table duringat least part of the pressing.

One or more embodiments of the present invention are applicable to anyimprint lithography process in which a patterned template is imprintedinto an imprintable medium in a flowable state, and for instance can beapplied to hot and UV imprint lithography as described above. For thepurpose of understanding one or more embodiments of the presentinvention, it is not necessary to describe the imprint process in anymore detail than has already been given and is known in the art.

Further features of one or more embodiments of the present inventionwill be apparent from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying schematic drawings in whichcorresponding reference symbols indicate corresponding parts, and inwhich:

FIG. 1a-1c illustrate examples of conventional soft, hot and UVlithography processes respectively;

FIG. 2 illustrates a two step etching process employed when hot and UVimprint lithography is used to pattern a resist layer;

FIG. 3 schematically illustrates a template and a typical imprintableresist layer deposited on a substrate; and

FIG. 4 schematically shows an embodiment of an imprint lithographicapparatus according to the invention;

FIG. 5 schematically shows an alternative embodiment of an imprintlithographic apparatus according to the invention;

FIG. 6 schematically shows a bottom view of the imprint template holderand imprintable medium dispensers of the left hand side of FIG. 5;

FIG. 7 schematically shows a close-up view of the left hand side of FIG.5 in operation.

DETAILED DESCRIPTION

There are two principal approaches to imprint lithography which will betermed generally as hot imprint lithography and UV imprint lithography.There is also a third type of “printing” lithography known as softlithography. Examples of these are illustrated in FIGS. 1a to 1 c.

FIG. 1a schematically depicts the soft lithography process whichinvolves transferring a layer of molecules 11 (typically an ink such asa thiol) from a flexible template 10 (typically fabricated frompolydimethylsiloxane (PDMS)) onto a resist layer 13 which is supportedupon a substrate 12 and planarization and transfer layer 12′. Thetemplate 10 has a pattern of features on its surface, the molecularlayer being disposed upon the features. When the template is pressedagainst the resist layer, the layer of molecules 11 stick to the resist.Upon removal of the template from the resist, the layer of molecules 11stick to the resist, the residual layer of resist is etched such thatthe areas of the resist not covered by the transferred molecular layerare etched down to the substrate.

The template used in soft lithography may be easily deformed and maytherefore not be suited to high resolution applications, e.g. on ananometer scale, since the deformation of the template may adverselyaffect the imprinted pattern. Furthermore, when fabricating multiplelayer structures, in which the same region will be overlaid multipletimes, soft imprint lithography may not provide overlay accuracy on ananometer scale.

Hot imprint lithography (or hot embossing) is also known as nanoimprintlithography (NIL) when used on a nanometer scale. The process uses aharder template made from, for example, silicon or nickel, which aremore resistant to wear and deformation. This is described for instancein U.S. Pat. No. 6,482,742 and illustrated in FIG. 1b . In a typical hotimprint process, a solid template 14 is imprinted into a thermosettingor a thermoplastic polymer resin 15, which has been cast on the surfaceof a substrate 12. The resin may, for instance, be spin coated and bakedonto the substrate surface or more typically (as in the exampleillustrated) onto a planarization and transfer layer 12′. It should beunderstood that the term “hard” when describing an imprint templateincludes materials which may generally be considered between “hard” and“soft” materials, such as for example “hard” rubber. The suitability ofa particular material for use as an imprint template is determined byits application requirements.

When a thermosetting polymer resin is used, the resin is heated to atemperature such that, upon contact with the template, the resin issufficiently flowable to flow into the pattern features defined on thetemplate. The temperature of the resin is then increased to thermallycure (e.g. crosslink) the resin so that it solidifies and irreversiblyadopts the desired pattern. The template may then be removed and thepatterned resin cooled.

Examples of thermoplastic polymer resins used in hot imprint lithographyprocesses are poly (methyl methacrylate), polystyrene, poly (benzylmethacrylate) or poly (cyclohexyl methacrylate). The thermoplastic resinis heated so that it is in a freely flowable state immediately prior toimprinting with the template. It is typically necessary to heatthermoplastic resin to a temperature considerably above the glasstransition temperature of the resin. The template is pressed into theflowable resin and sufficient pressure is applied to ensure the resinflows into all the pattern features defined on the template. The resinis then cooled to below its glass transition temperature with thetemplate in place whereupon the resin irreversibly adopts the desiredpattern. The pattern will consist of the features in relief from aresidual layer of the resin which may then be removed by an appropriateetch process to leave only the pattern features.

Upon removal of the template from the solidified resin, a two-stepetching process is typically performed as illustrated in FIGS. 2a to 2c. The substrate 20 has a planarization and transfer layer 21 immediatelyupon it, as shown in FIG. 2a . The purpose of the planarization andtransfer layer is twofold. It acts to provide a surface substantiallyparallel to that of the template, which helps ensure that the contactbetween the template and the resin is parallel, and also to improve theaspect ratio of the printed features, as described herein.

After the template has been removed, a residual layer 22 of thesolidified resin is left on the planarization and transfer layer 21,shaped in the desired pattern. The first etch is isotropic and removesparts of the residual layer 22, resulting in a poor aspect ratio offeatures where L1 is the height of the features 23, as shown in FIG. 2b. The second etch is anisotropic (or selective) and improves the aspectratio. The anisotropic etch removes those parts of the planarization andtransfer layer 21 which are not covered by the solidified resin,increasing the aspect ratio of the features 23 to (L2/D), as shown inFIG. 2c . The resulting polymer thickness contrast left on the substrateafter etching can be used as for instance a mask for dry etching if theimprinted polymer is sufficiently resistant, for instance as a step in alift-off process.

Hot imprint lithography suffers from a disadvantage in that not only isthe pattern transfer performed at a higher temperature, but alsorelatively large temperature differences might be required in order toensure the resin is adequately solidified before the template isremoved. Temperature differences between 35 and 100° C. may be needed.Differential thermal expansion between, for instance, the substrate andtemplate may then lead to distortion in the transferred pattern. Thismay be exacerbated by the relatively high pressure needed for theimprinting step, due the viscous nature of the imprintable material,which can induce mechanical deformation in the substrate, againdistorting the pattern.

UV imprint lithography, on the other hand, does not involve such hightemperatures and temperature changes nor does it require such viscousimprintable materials. Rather, UV imprint lithography involves the useof a partially or wholly transparent template and a UV-curable liquid,typically a monomer such as an acrylate or methacrylate. for example. Ingeneral, any photopolymerizable material could be used, such as amixture of monomers and an initiator. The curable liquid may also, forinstance, include a dimethyl siloxane derivative. Such materials areless viscous than the thermosetting and thermoplastic resins used in hotimprint lithography and consequently move much faster to fill templatepattern features. Low temperature and low pressure operation also favorshigher throughput capabilities. Although the name ‘UV imprintlithography’ implies that UV radiation is always used, those skilled inthe art will be aware that any suitable actinic radiation may be used(for example, visible light may be used). Hence, any reference herein toUV imprint lithography, UV radiation, UV curable materials, etc. shouldbe interpreted as including any suitable actinic radiation, and shouldnot be interpreted as being limited to UV radiation only.

An example of a UV imprint process is illustrated in FIG. 1c . A quartztemplate 16 is applied to a UV curable resin 17 in a similar manner tothe process of FIG. 1b . Instead of raising the temperature as in hotembossing employing thermosetting resins, or temperature cycling whenusing thermoplastic resins, UV radiation is applied to the resin throughthe quartz template in order to polymerize and thus cure it. Uponremoval of the template, the remaining steps of etching the residuallayer of resist are the same or similar as for the hot embossing processdescribed herein. The UV curable resins typically used have a much lowerviscosity than typical thermoplastic resins so that lower imprintpressures can be used. Reduced physical deformation due to the lowerpressures, together with reduced deformation due to high temperaturesand temperature changes, makes UV imprint lithography suited toapplications requiring high overlay accuracy. In addition, thetransparent nature of UV imprint templates can accommodate opticalalignment techniques simultaneously to the imprinting.

Although this type of imprint lithography mainly uses UV curablematerials, and is thus generically referred to as UV imprintlithography, other wavelengths of radiation may be used to cureappropriately selected materials (e.g., activate a polymerization orcross linking reaction). In general, any radiation capable of initiatingsuch a chemical reaction may be used if an appropriate imprintablematerial is available. Alternative “activating radiation” may, forinstance, include visible light, infrared radiation, x-ray radiation andelectron beam radiation. In the general description herein, referencesto UV imprint lithography and use of UV radiation are not intended toexclude these and other activating radiation possibilities.

As an alternative to imprint systems using a planar template which ismaintained substantially parallel to the substrate surface, rollerimprint systems have been developed. Both hot and UV roller imprintsystems have been proposed in which the template is formed on a rollerbut otherwise the imprint process is very similar to imprinting using aplanar template. Unless the context requires otherwise, references to animprint template include references to a roller template.

There is a particular development of UV imprint technology known as stepand flash imprint lithography (SFIL) which may be used to pattern asubstrate in small steps in a similar manner to optical steppersconventionally used, for example, in IC manufacture. This involvesprinting small areas of the substrate at a time by imprinting a templateinto a UV curable resin, ‘flashing’ UV radiation through the template tocure the resin beneath the template, removing the template, stepping toan adjacent region of the substrate and repeating the operation. Thesmall field size of such step and repeat processes may help reducepattern distortions and CD variations so that SFIL may be particularlysuited to manufacture of IC and other devices requiring high overlayaccuracy.

Although in principle the UV curable resin can be applied to the entiresubstrate surface, for instance by spin coating, this may be problematicdue to the volatile nature of UV curable resins.

One approach to addressing this problem is the so-called ‘drop ondemand’ process in which the resin is dispensed onto a target portion ofthe substrate in droplets immediately prior to imprinting with thetemplate. The liquid dispensing is controlled so that a certain volumeof liquid is deposited on a particular target portion of the substrate.The liquid may be dispensed in a variety of patterns and the combinationof carefully controlling liquid volume and placement of the pattern canbe employed to confine patterning to the target area.

Dispensing the resin on demand as mentioned is not a trivial matter. Thesize and spacing of the droplets are carefully controlled to ensurethere is sufficient resin to fill template features while at the sametime minimizing excess resin which can be rolled to an undesirably thickor uneven residual layer since as soon as neighboring drops touch fluid,the resin will have nowhere to flow.

Although reference is made herein to depositing UV curable liquids ontoa substrate, the liquids could also be deposited on the template and ingeneral the same techniques and considerations will apply.

FIG. 3 illustrates the relative dimensions of the template, imprintablematerial (curable monomer, thermosetting resin, thermoplastic, etc) andsubstrate. The ratio of the width of the substrate, D, to the thicknessof the curable resin layer, t, is of the order of 10⁶. It will beappreciated that, in order to avoid the features projecting from thetemplate damaging the substrate, the dimension t should be greater thanthe depth of the projecting features on the template.

The residual layer left after stamping is useful in protecting theunderlying substrate, but as mentioned herein it may also be the sourceof a problem, particularly when high resolution and/or minimum CD(critical dimension) variation is desired. The first ‘breakthrough’ etchis isotropic (non-selective) and will thus to some extent erode thefeatures imprinted as well as the residual layer. This may beexacerbated if the residual layer is overly thick and/or uneven. Thisproblem may, for instance, lead to variation in the thickness of linesultimately formed in the underlying substrate (i.e. variation in thecritical dimension). The uniformity of the thickness of a line that isetched in the transfer layer in the second anisotropic etch is dependantupon the aspect ratio and integrity of the shape of the feature left inthe resin. If the residual resin layer is uneven, then the non-selectivefirst etch can leave some of these features with “rounded” tops so thatthey are not sufficiently well defined to ensure good uniformity of linethickness in the second and any subsequent etch process. In principle,the above problem may be reduced by ensuring the residual layer is asthin as possible but this can require application of undesirably largepressures (possibly increasing substrate deformation) and relativelylong imprinting times (possibly reducing throughput).

The template is a significant component of the imprint lithographysystem. As noted herein, the resolution of the features on the templatesurface is a limiting factor on the attainable resolution of featuresprinted on the substrate. The templates used for hot and UV lithographyare generally formed in a two-stage process. Initially, the desiredpattern is written using, for example, electron beam writing (e.g., withan electron beam pattern generator), to give a high resolution patternin resist. The resist pattern is then transferred into a thin layer ofchrome which forms the mask for the final, anisotropic etch step totransfer the pattern into the base material of the template. Othertechniques such as for example ion-beam lithography, X-ray lithography,extreme UV lithography, epitaxial growth, thin film deposition, chemicaletching, plasma etching, ion etching or ion milling could be used.Generally, a technique capable of very high resolution will be used asthe template is effectively a 1× mask with the resolution of thetransferred pattern being limited by the resolution of the pattern onthe template.

The release characteristics of the template may also be a consideration.The template may, for instance, be treated with a surface treatmentmaterial to form a thin release layer on the template having a lowsurface energy (a thin release layer may also be deposited on thesubstrate).

Another consideration in the development of imprint lithography is themechanical durability of the template. The template may be subjected tolarge forces during stamping of the resist, and in the case of hotlithography, may also be subjected to extremes of pressure andtemperature. This may cause wearing of the template, and may adverselyaffect the shape of the pattern imprinted upon the substrate.

In hot imprint lithography, there is a potential advantage in using atemplate of the same or similar material to the substrate to bepatterned in order to reduce differential thermal expansion between thetwo. In UV imprint lithography, the template is at least partiallytransparent to the activation radiation and accordingly quartz templatesare used.

Although specific reference may be made in this text to the use ofimprint lithography in the manufacture of ICs, it should be understoodthat imprint apparatus and methods described may have otherapplications, such as the manufacture of integrated optical systems,guidance and detection patterns for magnetic domain memories, hard discmagnetic media, flat panel displays, thin-film magnetic heads, etc.

While in the description herein, particular reference has been made tothe use of imprint lithography to transfer a template pattern to asubstrate via an imprintable resin effectively acting as a resist, insome circumstances the imprintable material may itself be a functionalmaterial, for instance having a functionally such as electrical orthermal conductivity, optical linear or non-linear response, amongothers. For example, the functional material may form a conductivelayer, a semi-conductive layer, a dielectric layer or a layer havinganother desirable mechanical, electrical or optical property. Someorganic substances may also be appropriate functional materials. Suchapplications may be within the scope an embodiment of the presentinvention.

FIG. 4 shows schematically an imprint lithography apparatus according toan embodiment of the invention. The imprint lithography apparatuscomprises a first substrate table 31 and a second substrate table 32.The first substrate table 31 is provided with a gas (e.g., air) foot 33which rests upon a base plate 34 of the apparatus. The gas foot 34 isarranged such that gas at a predetermined pressure is passed to the gasfoot and establishes a cushion of gas which supports the gas foot on thebase plate 33. This allows the gas foot 34 and the substrate table 31 tomove smoothly over the base plate 34. The second substrate table 32 isalso provided with a gas foot 35.

A dispenser 36 configured to dispense imprintable medium is fixed to amounting 37. The imprintable medium dispenser 36 may be, for example, aninkjet nozzle which deposits droplets of imprintable medium. It may, forexample, comprise an array of inkjet nozzles. Suitable configurations ofinkjet nozzle arrays will be known to those skilled in the art.

A first alignment system 39, which may be, for example, an opticaldiffraction based system or an image recognition based system, isarranged to align one or more target portions of the first substrate 38with respect to one or more alignment marks provided on the firstsubstrate table 31. This may be done, for example, by determining aposition of an alignment mark on the first substrate 38 with respect toan alignment mark on the first substrate table 31.

A substrate 38, referred to as the first substrate, is provided on thefirst substrate table 31. The substrate 38 receives droplets ofimprintable medium deposited by the imprintable medium dispenser 36. Thedroplets of imprintable medium may be provided across the entire useablesurface of the substrate 38. Alternatively, the droplets may be providedon a pre-selected portion of the substrate 38.

The second substrate table 32 is located beneath an imprint template 40which is held in a template holder 41. A lowermost surface of theimprint template 40 is provided with a pattern. The imprint template 40and the template holder 41 are moveable in the Z-direction, as indicatedby the arrow located adjacent the imprint template holder. A substrate42, referred to as the second substrate, is provided on the secondsubstrate table 32.

In use, the imprintable medium dispenser 36 dispenses droplets ofimprintable medium onto the first substrate 38, at the same time thatthe imprint template 40 is imprinting a pattern onto the secondsubstrate 42. This process is described in more detail below.

Initially, there is no substrate provided on the first substrate table31. A substrate handler (not illustrated) passes a substrate onto thefirst substrate table 31. In FIG. 4 this substrate is the firstsubstrate 38. The first substrate 38 is positioned to within apredetermined accuracy on the first substrate table 31. This is so thatall desired useable areas of the first substrate 38 may be accuratelyreached by the imprintable medium dispenser 36, and at a later time bythe imprint template 40. A vacuum is applied through a multiplicity ofopenings provided in the first substrate table 31, thereby securing thefirst substrate 38 to the first substrate table such that it will notmove over the first substrate table.

The first alignment system 39 is used to determine the position of analignment mark on the first substrate 38 with respect to an alignmentmark on the first substrate table 31. This is done by translating thefirst substrate table 31 beneath the alignment system 39. Deviation ofthe position of a target portion from its expected position isdetermined. Since the first substrate 38 is firmly secured to the firstsubstrate table 31, the position of a target portion on the firstsubstrate with respect to an alignment mark on the first substrate table31 will not change following the alignment measurement.

The first substrate table 31 is translated through a predeterminedroute, such that all desired usable areas of the first substrate passbeneath the imprintable medium dispenser 36. The imprintable mediumdispenser 36 dispenses droplets of imprintable medium onto the firstsubstrate 38 while it is being translated through the predeterminedroute. The imprintable medium may be provided as arrays of droplets,formations of which will be apparent to those skilled in the art. Theprecise positions at which the droplets of imprintable medium areprovided on the first substrate 38 may be determined with reference tothe alignment measurement.

At the same time that imprintable medium is being provided on the firstsubstrate 38, a pattern is being imprinted onto the second substrate 42(the second substrate has already been provided with imprintablemedium).

A second alignment system 45, which may be, for example, an opticaldiffraction based system or an image recognition based system, is usedto measure the locations of one or more alignment marks provided on thesecond substrate table 32. This allows the position of a target portionof the second substrate 42 to be determined, so that it can be alignedwith the imprint template 40. Once a desired target portion has beenaligned with the imprint template 40, the template holder 41 is moveddownward in the Z-direction until it presses the imprint template 40into imprintable medium provided on the second substrate 42. The regionof imprintable medium located beneath the imprint template 40 is thenilluminated with UV radiation, which may be generated, for example, by aUV source 50.

The UV source 50, template holder 41, and imprint template 40 arearranged such that the UV radiation is only incident upon the portion ofimprintable medium which is located beneath the imprint template. Thismay be achieved, for example, by the use of one or more screens or byappropriate application of a coating to one or more sides of the imprinttemplate 40 and template holder 41 which is opaque to UV radiation. Itwill be appreciated by those skilled in the art that instead of UVradiation any suitable wavelength may be used to illuminate theimprintable medium (i.e. any suitable actinic radiation may be used).For ease of terminology the term ‘UV radiation’ will continue to be usedin this description.

Once the imprintable medium has been cured by the UV radiation, theimprint template holder 41 and imprint template 40 are moved upwards inthe Z-direction and away from the second substrate 42. The secondsubstrate table 32 is then moved such that a second target portion islocated beneath the imprint template. The imprint process is thenrepeated.

Instead of having an imprint template 40 which is dimensioned to imprinta single target portion of the second substrate 42, a larger imprinttemplate may be used. For example the imprint template may bedimensioned such that the entire second substrate 42, or a substantialportion of the second substrate, is imprinted with a pattern during asingle imprint process.

Once the imprinting of patterns onto the second substrate 42 has beencompleted, and dispensing of imprintable medium onto the first substrate38 has been completed, the substrate tables 31 and 32 are swapped overinto opposite positions. In an embodiment, this is achieved by movingthe substrate tables 31, 32 (using the gas feet 33, 35) in theY-direction so that they will not collide, then moving the firstsubstrate table 31 in the positive X-direction and moving the secondsubstrate table 32 in the negative X-direction. In general terms, thefirst substrate table moves from a first position located at or adjacentto the imprintable medium dispenser to a second position located at oradjacent to the imprint template holder. The second substrate tablemoves from the second position to the first position.

The precise locations of the substrate tables 31, 32 may be monitoredusing interferometers (not shown) when they are in the first and secondpositions. The interferometers may be arranged such that a first set ofinterferometers measure the position of the substrate table which is inthe first position, regardless of which specific substrate table thatis, and similarly a second set of interferometers measure the positionof the substrate table which is in the second position. Theinterferometers need not necessarily monitor the positions of thesubstrate tables 31, 32 during the entire position swapping process.

The vacuum applied by the second substrate table 32 is released, so thatthe second substrate 42 is removable from the second substrate table.The second substrate 42 is then removed from the second substrate table32 by the substrate handler. Following this a new substrate is placed onthe second substrate table 32. The new substrate is provided withimprintable medium using the imprintable medium dispenser 36, in themanner described above.

The first substrate 38 is located beneath the imprint template 40, whichis used to imprint a pattern onto the first substrate. Once depositingof imprintable medium onto the new substrate has been completed, andimprinting of the pattern onto the first substrate 38 has beencompleted, the substrate tables 31, 32 are once again swapped over intoopposite positions (this is done in the same way as described above).

The embodiment of the invention provides, for example, an increase ofthroughput, since imprintable medium may be provided on a givensubstrate at the same time that a pattern is being imprinted onto adifferent substrate.

An alternative embodiment of the invention is shown schematically inFIG. 5. The embodiment shown in FIG. 5 corresponds in large part to theright hand side of FIG. 4, the principle differences being firstly thatthe left hand and right hand sides of FIG. 5 are substantially the same,and secondly that dispensers configured to dispense imprintable mediumare provided at either side of each imprint template holder.

Referring first to the left hand side of FIG. 5, a substrate 142 is heldon a substrate table 134 which is located on a gas foot 135. An imprinttemplate holder 141 holds an imprint template 140. A UV source 150 isprovided above the imprint template holder 141, and an alignment system145 is provided to one side of the template holder. Imprintable mediumdispensers 146 are provided on either side of the template holder 141.

Referring to the right hand side of FIG. 5, a substrate 242 is held on asubstrate table 234 which is located on a gas foot 235. An imprinttemplate holder 241 holds an imprint template 240. A UV source 250 isprovided above the imprint template holder 241, and an alignment system245 is provided to one side of the template holder. Imprintable mediumdispensers 246 are provided on either side of the template holder 241.

The imprintable medium dispensers 146, 246 are shown viewed from belowin FIG. 6. Each imprintable medium dispenser 146, 246 is provided with aseries of inkjet nozzles 160. Although this is represented schematicallyas five openings in FIG. 6, it will be appreciated that any suitablenumber of inkjet nozzles may be used, and that these may be provided ina series of rows or in the form of an array instead of being provided asa single row. Other suitable apertures may be used instead of inkjetnozzles. Also shown in FIG. 6 is the underside of the imprint templateholder 141, 242 and the imprint template 140, 240.

Referring to FIGS. 5 to 7, in use the substrate table 134, 234 isscanned in the X-direction beneath the imprint template 140, 240. Duringthis scanning movement, imprintable medium is deposited onto a targetportion of the substrate 142, 242 using the inkjet nozzles 160 of theleft hand imprintable medium dispenser 146, 246. The supply ofimprintable medium from the inkjet nozzles 160 is stopped once thetarget portion has been covered with imprintable medium. This is shownschematically in FIG. 7, the layer of imprintable medium beingdesignated 161. The substrate table 134, 234 continues to move in theX-direction until the imprint template 140, 240 is located over thetarget portion of imprintable medium 161. The target portion of thesubstrate 142, 242 is thus located beneath the imprint template 140, 240directly after it passes beneath the imprintable medium dispenser 146,246. The imprint template 140, 240 is pressed into the imprintablemedium 161, which is then illuminated using the UV source 150, 250. Theimprint template 140, 240 is then removed from the imprintable medium161, and the substrate table 134, 234 is once again scanned in theX-direction to allow further imprintable medium to be applied to thesubstrate 142, 242.

The term ‘directly after’ is intended to mean that the target portiondoes not pass through a significant route (e.g. scans in the positiveand negative X-direction and translations in the Y-direction) before itis beneath the imprint template 140, 240. It is not intended to meanthat there is no separation between the imprintable medium dispenser146, 246 and the imprint template 140, 240.

When, at a subsequent time, the substrate table is 134, 234 is beingscanned in the negative X-direction, the right hand imprintable mediumdispenser 146, 246 is used to deposit imprintable medium onto thesubstrate 140, 240.

Referring to FIG. 5, substrates handlers (not illustrated) may beprovided at either side of the apparatus, to put substrates onto thesubstrate tables 134 and 234, and to remove the substrates from thesubstrate tables. Alternatively, a single substrate handler may be used,the substrate tables 134, 234 swapping positions, as shown schematicallyby the arrows in the center of FIG. 5, to allow the single substratehandler to put a substrate onto and remove a substrate from both thesubstrate tables.

Although two UV radiation sources 150, 250 are shown, these may bereplaced by a single source which is connected via suitable radiationpaths to both of the imprint templates 140, 240. In one arrangement theradiation path may be configured to allow simultaneous illumination ofboth substrates 142, 242. Where this is done, operation of the portionof apparatus on the left hand side of FIG. 5 and the portion ofapparatus of the right hand side of FIG. 5 is synchronized so that theillumination falls onto the substrates 142, 242 at the appropriate time(i.e. when the imprint templates 140, 240 are pressed onto thesubstrates).

In an alternative arrangement, the radiation path may be configured suchthat radiation may only pass to one substrate at a given time. Forexample this may be achieved by using a movable mirror. Where this isdone, the apparatus shown in the left hand side of FIG. 5 is operatedasynchronously with respect to the apparatus shown in the right handside of FIG. 5, such that the illumination falls upon the substrate atthe appropriate time. This arrangement allows a weaker UV radiationsource to be used, since radiation from the source is only sent to onesubstrate at any given time.

Although the imprintable medium dispensers 146, 246 are shown in FIGS. 5to 7 as being located on either X-direction side of the imprint templateholder 140, 240, it will be appreciated that the imprintable mediumdispensers may alternatively be located on either Y-direction side ofthe imprint template. The positions at which the imprintable mediumdispensers 146, 246 are located may be determined by considering thedirection(s) in which the substrate table 134, 234 will be moved, sothat imprintable medium is provided on a given target portion of thesubstrate 142, 242 before that target portion is beneath the imprinttemplate 140, 240.

In some instances it may be desired to provide the imprintable mediumdispensers on each side of the imprint template holder 141, 241.

The embodiment of the invention described in relation to FIGS. 5 to 7may provide an increased throughput because it allows imprinting of twosubstrates to occur simultaneously. In addition, it allows imprintablemedium to be provided on the substrates just before imprinting occurs.

The imprintable medium dispensers described in relation to FIGS. 5 to 7may be provided in an imprint lithography apparatus which includes onlyone substrate table.

In an embodiment, there is provided an imprint lithography apparatus,comprising: a first substrate table arranged to hold a substrate; asecond substrate table arranged to hold a substrate; an imprint templateholder arranged to hold an imprint template; and an imprintable mediumdispenser, wherein the first substrate table is moveable between a firstposition located at or adjacent to the imprintable medium dispenser, anda second position located at or adjacent to the imprint template holder,and wherein the second substrate table is moveable between the first andsecond positions, such that the first and second substrate tables swappositions.

In an embodiment, the apparatus further comprises a first alignmentsystem located at or adjacent the imprintable medium dispenser and asecond alignment system located at or adjacent to the imprint templateholder. In an embodiment, the first alignment system is arranged todetermine the location of one or more alignment marks on the firstsubstrate with respect to one or more alignment marks on the firstsubstrate table. In an embodiment, the second alignment system isarranged to determine the location of one or more alignment marks on thesecond substrate table, to allow one or more target portions of thesecond substrate to be aligned with the imprint template when held bythe imprint template holder. In an embodiment, the apparatus furthercomprises a set of interferometers arranged to monitor the locations ofthe substrate tables. In an embodiment, the apparatus comprises a firstset of interferometers arranged to monitor the location of whicheversubstrate table is at or adjacent to the imprintable medium dispenserand a second set of interferometers arranged to monitor the location ofwhichever substrate table is at or adjacent to the imprint templateholder. In an embodiment, the substrate tables are moveable in twodirections which both lie in a plane substantially perpendicular to anaxis of movement of the imprint template holder. In an embodiment, thesubstrate tables are each supported by a gas foot. In an embodiment, theimprintable medium dispenser comprises an inkjet nozzle, or an array ofinkjet nozzles.

In an embodiment, there is provided an imprint lithography apparatuscomprising: a first substrate table arranged to hold a substrate; asecond substrate table arranged to hold a substrate; an imprinttemplate; and a dispenser configured to dispense imprintable medium,wherein the first substrate table is moveable between a first positionlocated at or adjacent to the imprintable medium dispenser, and a secondposition located at or adjacent to the imprint template, and the secondsubstrate table is moveable between the first and second positions, suchthat the first and second substrate tables swap positions.

In an embodiment, there is provided an imprint lithography apparatus,comprising: a substrate table arranged to hold a substrate; an imprinttemplate holder arranged to hold an imprint template; and at least twoimprintable medium dispensers, a first of the imprintable mediumdispensers located at or adjacent to one side of the imprint templateholder, and a second of the imprintable medium dispensers located at oradjacent to an opposite side of the imprint template holder.

In an embodiment, the substrate table is moveable in a scanningdirection such that a target portion of the substrate is located beneaththe imprint template directly after it passes beneath one of theimprintable medium dispensers. In an embodiment, the imprintable mediumdispenser which is located upstream of the imprint template is arrangedto provide imprintable medium onto the substrate prior to the targetportion being located beneath the imprint template. In an embodiment, atleast one of the imprintable medium dispensers comprises a row ofapertures, a series of rows of apertures or an array of apertures. In anembodiment, the apertures are inkjet nozzles. In an embodiment, theapparatus further comprises two additional imprintable mediumdispensers, such that an imprintable medium dispenser is located at oradjacent to each side of the imprint template holder. In an embodiment,the apparatus further comprises: a second substrate table arranged tohold a second substrate; a second imprint template holder arranged tohold a second imprint template; and at least two imprintable mediumdispensers, a first of the imprintable medium dispensers located at oradjacent to one side of the second imprint template holder, and a secondof the imprintable medium dispensers located at or adjacent to anopposite side of the second imprint template holder. In an embodiment,the positions of the first and second substrate tables may be swapped.

In an embodiment, there is provided an imprint lithography apparatus,comprising: a substrate table arranged to hold a substrate; an imprinttemplate; and at least two imprintable medium dispensers, a first of theimprintable medium dispensers located at or adjacent to one side of theimprint template, and a second of the imprintable medium dispenserslocated at or adjacent to an opposite side of the imprint template.

In an embodiment, there is provided an imprint lithography process,comprising: moving a first substrate table holding a first substrate toa first position; aligning the substrate to the substrate table at thefirst position; dispensing an imprintable medium layer on the firstsubstrate at the first position; moving the first substrate to a secondposition; moving a second substrate table holding a second substrate tothe first position; pressing, at the second position, one or moretemplates in the imprintable medium layer; and aligning the secondsubstrate to the second substrate table during at least part of thepressing.

While specific examples of the invention have been described above, itwill be appreciated that the present invention may be practicedotherwise than as described. The description is not intended to limitthe invention.

The invention claimed is:
 1. A method of using an imprint lithographyapparatus, wherein the imprint lithography apparatus comprises: asubstrate table to hold a substrate, an imprint template holder to holdan imprint template, and a dispensing system comprising at least twoimprintable medium dispensers, a first of the imprintable mediumdispensers located at or adjacent to one side of the imprint templateholder, and a second of the imprintable medium dispensers located at oradjacent to an opposite side of the imprint template holder, wherein atleast one of the at least two imprintable medium dispensers is arrangedto dispense a plurality of discrete droplets of imprintable medium ontothe substrate, the method comprising: controlling and causing the firstimprintable medium dispenser to dispense imprintable medium for movementof the substrate table in a first direction and not in a seconddirection different than the first direction; and controlling andcausing the second imprintable medium dispenser to dispense imprintablemedium for movement of the substrate table in the second direction andnot in the first direction.
 2. The method of claim 1, comprising movingthe substrate table in a scanning direction such that a target portionof the substrate is located beneath the imprint template directly afterit passes beneath one of the imprintable medium dispensers.
 3. Themethod of claim 2, wherein the imprintable medium dispenser which islocated upstream of the imprint template provides imprintable mediumonto the substrate prior to the target portion being located beneath theimprint template.
 4. The method of claim 1, comprising dispensing theimprintable medium from a row of apertures, a series of rows ofapertures or an array of apertures of at least one of the imprintablemedium dispensers.
 5. The method of claim 4, wherein the apertures areinkjet nozzles.
 6. The method of claim 1, further comprising using twoadditional imprintable medium dispensers to dispense imprintable medium,such that the imprintable medium dispensers are spaced around theimprint template holder and an imprintable medium dispenser is locatedat or next to each side of a plurality of sides of the imprint templateholder.
 7. The method of claim 1, further comprising: using a secondsubstrate table of the imprint lithography apparatus to hold a secondsubstrate; using a second imprint template holder of the imprintlithography apparatus to hold a second imprint template; and using atleast one imprintable medium dispenser of the imprint lithographyapparatus to dispense imprintable medium onto the second substrate. 8.The method of claim 7, comprising using at least two imprintable mediumdispensers of the imprint lithography apparatus to dispense imprintablemedium onto the second substrate, a first of the at least twoimprintable medium dispensers located at or adjacent to one side of thesecond imprint template holder, and a second of the at least twoimprintable medium dispensers located at or adjacent to an opposite sideof the second imprint template holder.
 9. The method of claim 7, furthercomprising swapping the positions of the first and second substratetables.
 10. The method of claim 7, further comprising causing the atleast one imprintable medium dispenser of the imprint lithographyapparatus to dispense imprintable medium onto the second substrate at atime when the first imprint template is imprinted into the imprintablemedium on the first substrate.
 11. A method of using an imprintlithography apparatus, wherein the imprint lithography apparatuscomprises: an imprint template, and a dispensing system comprising atleast two imprintable medium dispensers, a first of the imprintablemedium dispensers located at or adjacent to one side of the imprinttemplate, and a second of the imprintable medium dispensers located ator adjacent to an opposite side of the imprint template, wherein atleast one of the at least two imprintable medium dispensers is arrangedto dispense a plurality of discrete droplets of imprintable medium ontothe substrate, the method comprising: controlling and causing the firstimprintable medium dispenser to dispense imprintable medium for movementof the substrate in a first direction and not in a second directiondifferent than the first direction; and controlling and causing thesecond imprintable medium dispenser to dispense imprintable medium formovement of the substrate in the second direction and not in the firstdirection.
 12. The method of claim 11, comprising moving the substratein a scanning direction such that a target portion of the substrate islocated beneath the imprint template directly after it passes beneathone of the imprintable medium dispensers.
 13. The method of claim 12,wherein the imprintable medium dispenser which is located upstream ofthe imprint template provides imprintable medium onto the substrateprior to the target portion being located beneath the imprint template.14. The method of claim 11, comprising dispensing the imprintable mediumfrom a row of apertures, a series of rows of apertures or an array ofapertures of at least one of the imprintable medium dispensers.
 15. Themethod of claim 14, wherein the apertures are inkjet nozzles.
 16. Themethod of claim 11, further comprising using two additional imprintablemedium dispensers to dispense imprintable medium, such that theimprintable medium dispensers are spaced around the imprint templateholder and an imprintable medium dispenser is located at or next to eachside of a plurality of sides of the imprint template holder.
 17. Themethod of claim 11, further comprising: moving a second substrate in theimprint lithography apparatus; using a second imprint template of theimprint lithography apparatus; and using at least one imprintable mediumdispenser of the imprint lithography apparatus to dispense imprintablemedium onto the second substrate.
 18. The method of claim 17, comprisingusing at least two imprintable medium dispensers of the imprintlithography apparatus to dispense imprintable medium, a first of the atleast two imprintable medium dispensers located at or adjacent to oneside of the second imprint template, and a second of the at least twoimprintable medium dispensers located at or adjacent to an opposite sideof the second imprint template.
 19. The method of claim 17, furthercomprising swapping the positions of the first and second substratetables.
 20. The method of claim 17, further comprising causing the atleast one imprintable medium dispenser of the imprint lithographyapparatus to dispense imprintable medium onto the second substrate at atime when the first imprint template is imprinted into the imprintablemedium on the first substrate.